Research of voltage sag detection methods based on DSP

Voltage sag is a serious power quality problem,the voltage sag can be detected and analyzed online using the power quality monitoring device based on DSP. The paper presents some methods to detect the characteristics of voltage sag, such as root-mean-square(RMS), dq conversation of instantaneous voltage and its improved αβ-dq transform method, which are verified in the DSP and the results are correct.These ways all have the problem of time delay when detecting voltage sag, and different sag depths correspond to different detection delay time. According to the delay problems of voltage sags detection, the paper obtains the delay error curve of the starting time of voltage sags. In order to obtain more accurate starting time of voltage sags, these curves can be used to correct the error. The simulation results verify that the curves can correct the error time.